Heat Exchanger Networks - Network Design

When considering heat exchanger and network design, the important issue of data extraction was highlighted, as lost opportunities can result from poor data extraction in heat exchanger and network design. Similarly, there are fundamental issues associated with data extraction for the design of water systems. 

The pinch analysis method provides the targets for the Heat Exchange Network (HEN) designs of the examined process. This HEN design problem is complex and involves combinatorial problems in the pairing between the hot and cold streams to enhance the heat recovery [28]. HEN design is one of the most fundamental activities in the process design procedure as it is considered as sub-synthesis problem of the overall synthesis problem. 

List all the costs that are affected by changing the minimum tenperature approach in a heat-exchanger network (HEN) design. 

Of course, some processes do not require a reactor, e.g., some oil refinery processes. Here, the design starts with the sepauration system and moves outward to the heat exchanger network and utilities. However, the basic hierarchy prevails. 

Having found the best nonintegrated sequence, most designers would then heat integrate. In other words, the total problem is not solved simultaneously but in two steps. Moving outward from the center of the onion (see Fig. 1.6), the separation layer is addressed first, followed by the heat exchanger network layer. 

The energy cost of the process can be set without having to design the heat exchanger network and utility system. These energy targets cam be calculated directly from the material and energy balance. Thus... 

Let us take each of these components in turn and explore whether they can be accounted for from the material and energy balance without having to perform heat exchanger network design. 

Figure 7.9 The Xp parameter avoids steep slopes on the Fp curves, whereas minimum Fp does not. (Reprinted from Ahmad, Linnhoff, and Smith, Cost Optimum Heat Exchanger Networks II. Targets and Design for Detailed Capital Cost Models, Computers Chem, Engg., 7 751, 1990 with permission from Elsevier Science, Ltd.)...

The design of the heat exchanger network is greatly simplified if the design is initialized with an optimized value for... 

Once a design is known for the first two layers of the onion (i.e., reactors and separators only), the overall total cost of this design for all four layers of the onion (i.e., reactors, separators, heat exchanger network, and utilities) is simply the total cost of all reactors and separators (evaluated explicitly) plus the total cost target for heat exchanger network and utilities. 

Ahmad, S., and Smith, R., Targets and Design for Minimum Number of Shells in Heat Exchanger Networks, IChemE, ChERD, 67 481, 1989. 

Having explored the major degrees of freedom, the material and energy balance is now fixed, and hence the hot and cold streams which contribute to the heat exchanger network are firmly defined. The remaining task is to complete the design of the heat exchanger network. 

Heat Exchanger Network Design Based on the Optimization of a Reducible Structure... 

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